Battery system

ABSTRACT

A control unit for a battery system includes a plurality of battery cells is provided. The control unit includes: an input node configured to receive a sensor signal indicative of a state of at least one of the plurality of battery cells; a microcontroller connected to the input node and configured to generate a first control signal based on the sensor signal; and a switch control circuit configured to control a power switch of the battery system by: receiving the sensor signal, the first control signal, and a fault signal indicative of an operational state of the microcontroller; generating a second control signal based on the sensor signal; and transmitting one of the first control signal and the second control signal to an output node of the control unit based on the received fault signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/367,015, filed on Mar. 27, 2019, which claims priority to and thebenefit of European Patent Application No. 18182603.3, filed in theEuropean Patent Office on Jul. 10, 2018, and Korean Patent ApplicationNo. 10-2018-0136028, filed in the Korean Intellectual Property Office onNov. 7, 2018, the entire content of all of which are incorporated hereinby reference.

BACKGROUND 1. Field

Aspects of embodiments of the present invention relate to a batterysystem including an integrated redundant relay control for disconnectingthe battery system from an external load. Additional aspects ofembodiments of the present invention relate to a control unit for abattery system providing the redundant relay control and to a method foroperating a battery system by using the control unit.

2. Description of the Related Art

A rechargeable or secondary battery differs from a primary battery inthat it is designed to be repeatedly charged and discharged, while thelatter is only designed for an irreversible conversion of chemical toelectrical energy. Low-capacity rechargeable batteries are used as powersupplies for small electronic devices, such as cellular phones, notebookcomputers, and camcorders, while high-capacity rechargeable batteriesare used as power supplies for hybrid vehicles and the like.

In general, rechargeable batteries include an electrode assemblyincluding a positive electrode, a negative electrode, and a separatorinterposed between the positive and negative electrodes, a casereceiving (or accommodating) the electrode assembly, and an electrodeterminal electrically connected to the electrode assembly. Anelectrolyte solution is injected into the case to enable charging anddischarging of the battery via an electrochemical reaction between thepositive electrode, the negative electrode, and the electrolytesolution. The shape of the case, for example, cylindrical orrectangular, etc., depends on the battery's intended purpose.

Rechargeable batteries may be a battery module including multiplebattery submodules, each including battery cells coupled to each otherin series and/or parallel to provide high energy density for, as oneexample, a hybrid vehicle. Such battery modules may be mechanically andelectrically integrated, equipped with a thermal management system, andconfigured to communicate with each other and with one or moreelectrical consumers to form a battery system.

Static control of battery power output and charging may not besufficient to meet the dynamic power demands of various electricalconsumers connected to the battery system. Thus, steady or intermittentexchange of information between the battery system and the controllersof the electrical consumers may be used. This information may includethe battery system's actual state of charge (SoC), potential electricalperformance, charging ability, and internal resistance, as well as theconsumers' actual or predicted power demands or surpluses.

For monitoring, controlling, and/or setting the aforementionedparameters, a battery system may include a battery management unit (BMU)and/or a battery management system (BMS). Such control units may be anintegral part of the battery system and may be disposed within a commonhousing or may be part of a remote control unit communicating with thebattery system via a suitable communication bus. In both cases, thecontrol unit may communicate with the electrical consumers via asuitable communication bus, such as a controller area network (CAN) orserial peripheral interface (SPI).

The BMS/BMU may further communicate with each of the battery submodules,for example, with a cell supervision circuit (CSC) of each of thebattery submodules. The CSC may be further connected to a cellconnection and sensing unit (CCU) of one or more of the batterysubmodules that may interconnect the battery cells of the respectivebattery submodule.

A battery system may further include a protection system to providevoltage level control of a power interface of the battery system and toenable fast and reliable safety shutdown of the power interface in theevent of non-permissible operating conditions. Such protection systemsmay be adapted to shut down (or cut off) a power connection between thebattery system and an external terminal of the battery system.Generally, a protection system may include an electro-mechanical switchcontrolled by a microcontroller (MCU) of the battery system.

Typically, the microcontroller controlling such electro-mechanicalswitches is also configured to control other functions of the batterysystem. For example, the MCU may be part of the BMS/BMU of the batterysystem to provide further integration of the battery system, whichreduces the battery system's material costs and the construction spacerequirements.

However, as battery systems' capacities increase, especially those usedin partially electrically powered vehicles, the high voltage (HV)batteries increasingly supply power to security (and safety) relevantfunctions of the vehicle, such as steer-by-wire systems, autonomousdriving systems, and/or crash prevention and mitigation systems. Thus,the availability and reliability of the HV batteries is becoming moreimportant because they power security relevant functions. For example,some manufacturers already rank the availability of the HV batteriesaccording to the automotive safety integrity level (ASIL) B standard.

A failure rate of the battery system should be sufficiently low toensure safe operation. For example, for a battery system to meet theASIL B standard, it must have a fit rate of 100 FIT (“failure in time”,i.e., failures per 10⁹h) or below. These specifications have beenrelatively difficult to achieve due to the microcontrollers generallyutilized in the control units of battery systems, such as in MCU orSystem Basis Chip (SBS). For example, the MCU used in a common BMS/BMUsmay have a fit rate of up to 2000 FIT and, accordingly, may not beapproved under the ASIL B standard.

SUMMARY

One or more of drawbacks of the related art may be avoided or at leastmitigated according to embodiments of the present invention. Accordingto one embodiment of the present invention, a control unit for a batterysystem is provided, and the control unit includes an input nodeconfigured to receive a sensor signal, which is indicative of a state ofat least one of a plurality of battery cells of the battery system. Forexample, the control unit is configured to monitor the state of thebattery system by monitoring at least some of the battery cells. Thesensor(s) supplying the sensor signal(s) is (are) part of either thecontrol unit or the battery system. The input node may be configured forsingle-ended or differential input.

The control unit further includes a microcontroller that is connected tothe input node and is configured to generate a first control signalbased on the sensor signal. The first control signal is used to controla power switch, such as a relay, of the battery system in which thecontrol unit is provided. In one embodiment, the first control signal isused to set the power switch into either a conductive or anon-conductive state by, for example, having one of two values. Thus,the microcontroller is configured to control the protection system ofthe battery system. The protection system may, for example, perform anovercurrent protection function. The sensor signal may refer to acurrent provided by the battery system. The microcontroller may providefurther control functions with respect to the battery system. Forexample, in one embodiment, the microcontroller is also utilized as aBMS/BMU as described above.

In some embodiments, the control unit is also configured to perform acontrol function with respect to at least one, but up to all of, thebattery cells of the battery system. The control functions relate tomeasurements of cell voltages, cell currents, cell resistances, or cellcapacities. In some embodiments, the control functions also relate tothe active or passive balancing of cell voltages or cell currents of aplurality of the battery cells. The control functions may further relateto data communication with the CSCs of the battery cells or batterysubmodules of the battery system and with electrical consumers.

The control unit may further include a switch control circuit configuredto control a power switch of the battery system. The control unit mayinclude an output node for supplying a control signal to the powerswitch. The control signal may be used to set the power switch intoeither a conductive or a non-conductive state. The control signal may beused to freely set the state (e.g., the conductivity state) of the powerswitch. For example, the switch control circuit may be configured toreceive the first control signal from the microcontroller and the sensorsignal from the input node.

The switch control circuit may be further configured to receive a faultsignal that is indicative of an operation state (e.g., an operationalstate) of the microcontroller. In one embodiment, the fault signal isgenerated and output by (e.g., received from) the microcontrolleritself. In other embodiments, the fault signal is generated and outputby an additional circuit or component that is configured to monitor themicrocontroller, such as a system basis chip (SBC).

The switch control circuit is further configured to generate a secondcontrol signal based on the sensor signal. The second control signal maybe configured to control a power switch, for example, a relay, of thebattery system in which the control unit is provided. In one embodiment,the second control signal is used to set the power switch into either aconductive or a non-conductive state by, for example, having one of twovalues. In other embodiments, the second control signal is configured tofreely set the conductivity state of the power switch. In oneembodiment, the second control signal is generated by comparing thesensor signal to a threshold value (e.g., a predetermined thresholdvalue).

According to an embodiment of the present invention, the switch controlcircuit is configured to transmit one of the first control signal andthe second control signal to an output node of the control unit based onthe received fault signal. For example, the switch control circuit isconfigured to control the power switch via the output node bytransmitting either the first control signal or the second controlsignal, which are both suitable to set the power switch into either aconductive or a non-conductive state. Thus, the switch control circuit,according to an embodiment of the present invention, provides twoprimary functions: (a) generating a second control signal in addition toa control signal generated by the microcontroller; and (b) multiplexingthe first and second control signals.

The control unit provides a bypass to a microcontroller, which iscommonly used to control a power switch for emergency shut-down of abattery system. Accordingly, the availability of the battery system isimproved by decreasing the failure in time (FIT) rate of the batterysystem, particularly of the protection system of the battery system, byproviding an alternative signal path between a security relevant sensorvalue and a power switch. The control unit allows automotive safetyintegrity level (ASIL) B classification of a battery system.

In one embodiment, the control unit further includes a front endcircuit, such as an analog front end (AFE) circuit, that is connected tothe input node and is configured to generate a state signal based on thesensor signal. In one embodiment, the state signal is equal to a sensorsignal, which may be selected by a multiplexer. However, the front endcircuit may include one or more of an analog amplifier, an operationamplifier, filters, and/or an analog-to-digital converter. Thus, thestate signal may be a signal processed by the front end circuit havingimproved signal-to-noise (S/N) ratio and decreased disturbances and maybe amplified with respect to a reference voltage (e.g., a predeterminedreference voltage or a baseline voltage) or may be previously convertedto a digital signal. Various front end circuits suitable for receivingdifferent sensor signal inputs are generally known in the relevant art.When the front end circuit is part of the control unit, the sensorsignal is replaced by the state signal downstream from the front endcircuit. In the following embodiments, only a control unit including afront end circuit is described, but the present invention is not limitedto this arrangement.

According to one embodiment, the switch control circuit is configured totransmit the first control signal to the output node (e.g., to the powerswitch) when the received fault signal is indicative of operability ofthe microcontroller (e.g., when the microcontroller is operable). Inother words, during a normal mode of the microcontroller without afailure occurring therein, the microcontroller controls the power switchof the battery system. Thus, all functionalities and safety mechanisms,such as those with respect to a plurality of different sensor values(e.g., temperature, current, voltage, gas composition, etc.) may beutilized to control an emergency shut down of the battery system.

The switch control circuit may be configured to transmit the secondcontrol signal to the output node (e.g., to the power switch) when thefault signal is indicative of a malfunction of the microcontroller(e.g., when the microcontroller is malfunctioning). In other words, whena failure occurs in the microcontroller, the control of the power switchvia the microcontroller is stopped and the power switch is insteadcontrolled by the switch control circuit. Thus, even in a faultsituation of the microcontroller, reliable emergency shut down of thebattery system is provided. The control via the switch control circuitmay be based on fewer sensor signals, for example, only current sensorsignals.

The above-described embodiments provide a basic solution for controllingthe power switch with the switch control circuit instead of by themicrocontroller. In some embodiments, the switch control circuit may beconfigured to consider further input signals, such as signals indicativeof an operational state of the vehicle or the battery system, signalsindicative of environmental conditions, and/or signals indicative of anoperational state of the switch control circuit, before switching thecontrol signal. Further, time constants may be applied before switchingthe control signals from the first control signal to the second controlsignal. An exemplary embodiment of a battery system for an electricvehicle is described in more detail below.

According to another embodiment, the control unit further includes anamplification circuit that is interconnected between the front endcircuit and the switch control circuit. In some embodiments, theamplification circuit is interconnected between at least one of theinput nodes of the control unit and the switch control circuit. Theswitch control circuit may be further configured to generate the secondcontrol signal based on the amplified sensor signal. These embodimentsallow the second control signal to be derived directly from the statesignal or even from the sensor signal directly without any furtheramplification by the switch control circuit. Thus, amplifying the signalin the amplification circuit allows solely hardware components to beused without any additional programmable integrated circuits downstreamfrom the amplification circuit. When the sensor signals are amplified,another bypass around the front end circuit is provided for when afailure of the microcontroller is due to a cause that also influencesthe front end circuit, such as electro-magnetic interference.

In one embodiment of the control unit, the switch control circuit isconfigured as a hardware path. For example, the switch control circuitdoes not include any programmable components or integrated circuits,such as ASICs or MCUs, but only includes relatively simple electronichardware components, such as voltage dividers, transistors, resistors,capacitors, operational amplifiers, and/or electronic hardwarecomponents with comparable functionality and/or formed of theaforementioned components. Thus, the switch control circuit hasrelatively fast reaction and switching times with high reliability. Forexample, the switch control circuit may have a FIT rate of 100 or less.Further, the entire hardware path between the input nodes and the outputnode of the control unit is configured as a hardware path with a FITrate of 100 or less. One skilled in the relevant art is aware of how todetermine FIT rates of a hardware path based on the FIT rate of itscomponents.

In one embodiment, the control unit further includes a system basis chip(SBC) that is configured to monitor the microcontroller. The systembasis chip may be further configured to generate the fault signal and totransmit the fault signal to the switch control circuit. The systembasis chip may be configured to generate a fault signal indicative of amalfunction of the microcontroller in response to detecting amalfunction of the microcontroller and to generate a fault signalindicative of an operability of the microcontroller otherwise. Thesystem basis chip may be configured to perform additional functions,such as supervision functions, reset generators, watchdog functions, businterface (LIN, CAN, etc.), wake-up logic, and/or power switches.Further, the power switch, which is controlled by the control unit, maybe a relay. These embodiments further increase the reliability of thecontrol unit and thereby increase protection of the battery system.

Another embodiment of the present invention relates to a battery systemthat includes a plurality of battery cells that are electricallyconnected in series between a first node and a second node, a powerswitch that is interconnected between the first node or the second nodeand at least one external load, and a control unit according to theabove-described embodiments. The output node of the control unit isconnected to the power switch to control the conductivity of the powerswitch. The battery system, according to an embodiment of the presentinvention, utilizes the positive effects provided by the control unit.

According to one embodiment of the present invention, the switch controlcircuit is configured to set the power switch into a non-conductivestate after a first time period after receiving a fault signalindicating a malfunction of the microcontroller. In other words, theswitch control circuit shuts off the battery system from any externalload after a first time period (e.g., a fixed first time period) lapsesafter an error of the microcontroller has been detected. The shut offvia the power switch occurs irrespective of any other signal inputs tothe switch control circuit. Thus, when the switch control circuitdetects a fault of the microcontroller, the switch control circuit maycount (or start) the first time period for switching the power switch toa non-conductive state by starting a first timer. This functionalityprovides a reliable shut down mechanism for a microcontroller failureand, hence, allows for a low FIT rate and a high ASIL rating of acontrol unit according to embodiments of the present invention.

According to another embodiment of the present invention, the switchcontrol circuit is configured to generate a second control signal thatcauses the power switch to be set to a non-conductive state when thesensor signal (e.g., the state signal) exceeds a threshold (e.g., apredetermined threshold). Therefore, the switch control circuit mayinclude at least one comparator circuit or operational amplifier thatreceives the sensor signal (e.g., the state signal) as a first input andoutputs the second control signal. The threshold may be supplied to thecomparator or operational amplifier as a second input by an externalsignal or by an internal memory. Hence, the switch control circuit alsoprovides sensor-based emergency shutdown of the power switch (and of thebattery system). Such emergency shutdown is additional to thetimer-based shutdown, for example, it may only occur during the firsttime period.

According to a further embodiment of the present invention, the switchcontrol circuit is configured to set the power switch into a conductivestate for a second time period after receiving a fault signal indicatinga malfunction of the microcontroller. In other words, the switch controlcircuit generates and transmits a (third) control signal to set thepower switch into a conductive state to the output node (e.g., the powerswitch) for a second time period (e.g., a fixed second time period)starting with the detection of an error of the microcontroller. Thepower switch may be set to a conductive state irrespective of any othersignal inputs to the switch control circuit during the second timeperiod. Thus, the sensor-based emergency shut-down of the switch controlcircuit is postponed during the second time period and a shut-down ofthe power switch (and of the battery system) is prevented.

These features allow for a transition phase between normal operation ofthe control unit and the battery system controlled by the MCU and anavailability mode in which the control unit and the battery system arecontrolled by the switch control circuit after a fault of themicrocontroller occurs and before a sensor-based emergency shutdown isrealized by the switch control circuit. In some embodiments, the secondtime period is less than the fault tolerant time interval (FTTI) of theplurality of battery cells and/or less than the first time period. Thisensures that the battery system reaches a safe state by applying thehardware-controlled sensor-based emergency shutdown by the switchcontrol circuit within the fault tolerant time interval.

According to another embodiment, the battery system further includes atleast one sensor that is configured to detect at least one of a current,a voltage, and a temperature of at least one of the plurality of batterycells as a sensor signal. In other words, the at least one sensor signaland/or the state signal is based on at least one of a voltage, atemperature, and a current of at least one of the plurality of batterycells. Further, the at least one sensor may include a shunt resistorconnected in series with one of the first and second node. The controlunit thus includes two input nodes for receiving a voltage drop over theshunt as sensor signal indicative of a battery current. The two inputnodes may then be connected to the front end circuit and the switchcontrol circuit.

Another embodiment of the present invention relates to a vehicle, suchas an electric vehicle or hybrid vehicle, which includes at least onefirst electrical consumer electrically connected as an external load toa battery system according to the above-described embodiments . Hence,when a failure of the battery system's microcontroller occurs, anemergency shutdown of the first electrical consumer is controlled by theswitch control circuit. Thus, the reliability of the battery system,particularly its emergency shutdown, is improved.

The vehicle may further include at least one second electrical consumerthat is electrically connected to the battery system and that is notsecurity relevant for the vehicle. The vehicle may further include acontrol unit that is configured to shut off the at least one secondelectrical consumer in response to receiving a fault signal indicativeof a malfunction of the microcontroller. In one embodiment, the controlunit may be a system basis chip of the battery system's control unit asdescribed above. This embodiment allows the second electrical consumersof the vehicle to be immediately shut down upon recognition of a faultof the battery system's microcontroller. Particularly, high loadconsumers, such as the electric motor of the vehicle, are shut down asthe second electrical consumer. Hence, a current drawn from the batterysystem is quickly reduced for safety reasons. Further, as the firstelectrical consumers are security relevant for the vehicle, controllingthem by the hardware path switch control circuit as described aboveprovides prolonged availability of the security relevant functions ofthe first electrical consumers.

The first time period, the second time period, and the sensor-basedemergency shutdown as described above may be applied to the hardwarecontrol of the first electrical consumers after the microcontrollerfault recognition. Thus, the security relevant functions of the firstelectrical consumers are provided during the first time period (e.g., apredetermined first time period), and a sensor based emergency shut-downis also provided during the first time period but not during the secondtime period in order to allow for a transition into the safe state.

Another embodiment of the present invention relates to a method foroperating a battery system. The battery system includes a plurality ofbattery cells that are electrically connected in series between a firstnode and a second node, a power switch that is interconnected betweenthe first node or the second node and at least one external load, and acontrol unit that is configured to control the power switch.

In a first step, at least one sensor of the battery system detects atleast one sensor signal that is indicative of a state of at least one ofthe plurality of battery cells. This detection may occur during theentire operation time of the battery system, for example, during normaland availability mode. Further, the sensor signal may relate to at leastone of a current, voltage, and temperature of at least one battery cellof the plurality of battery cells.

Then, a microcontroller of the control unit determines a first controlsignal for controlling the power switch based on the sensor signal. Thefirst control signal is used to control the power switch as describedabove. This step is primarily performed during normal mode, that is, aslong as no fault of the microcontroller occurs. However, in someembodiments, this step may be performed after a fault of themicrocontroller has occurred.

The switch control circuit of the control unit receives the sensorsignal and the first control signal as described above and a faultsignal that is indicative of an operational state of themicrocontroller. The fault signal may be received by the microcontrolleritself or by another controller, such as a system basis chip, asdescribed above. The switch control circuit then generates a secondcontrol signal based on the sensor signal, and the second control signalis used to control the power switch as described above. According to anembodiment of the preset invention, the switch control circuit transmitsonly one of the first control signal and the second control signal tothe power switch via the output node of the control unit based on thereceived fault signal, for example, based on the value of the faultsignal.

In some embodiments, the switch control circuit transmits the firstcontrol signal to the output node (e.g., to the power switch) when thereceived fault signal is indicative of an operability of themicrocontroller. Further, the switch control circuit transmits thesecond control signal to the output node (e.g., to the power switch)when the fault signal is indicative of a malfunction of themicrocontroller. Hence, during the normal mode without a failureoccurring in the microcontroller, the microcontroller controls the powerswitch of the battery system, and when a failure occurs in themicrocontroller, the control of the power switch via the microcontrolleris stopped and the power switch becomes controlled solely by the switchcontrol circuit.

Thus, in the normal mode, all functionalities and safety mechanisms withrespect to a plurality of different sensor values (e.g., temperature,current, voltage, gas composition, etc.) may be utilized to control theemergency shut down of the battery system. However, even in a faultsituation of the microcontroller, a reliable emergency shut down of thebattery system is provided, even though it may be based on fewer sensorsignals, such as only a current sensor value.

In one embodiment of the present method, a front end circuit of thecontrol unit determines a state signal based on the sensor signal. Thestate signal is a processed sensor signal that is suitable for furtherprocessing by either the microcontroller or the switch control circuitas described in more detail above. When the front end circuit performsthat step, the sensor signal in the method as described above isreplaced by the state signal downstream from the front end circuit.

According to one embodiment, the method further includes at least one ofthe following steps performed by the switch control circuit of thecontrol unit.

The switch control circuit may set the power switch to be in anon-conductive state after a first time period after receiving a faultsignal indicating a malfunction of the microcontroller. Hence, areliable emergency shut-down is provided even when a microcontrollerfault occurs. The switch control circuit may set the power switch into aconductive state for a second time period (e.g., a predetermined secondtime period) after receiving a fault signal indicative of a malfunctionof the microcontroller. The transmission of the first control signaloccurs irrespective of the sensor signal and state signal. Hence, atransition period can be provided for transferring shut-down controlform the microcontroller to the switch control circuit.

Further, the switch control circuit may generate, during the first timeperiod, a second control signal that causes the power switch to be setinto a non-conductive state when the state signal exceeds a threshold(e.g., a predetermined threshold). Hence, a sensor-based emergencyshut-down is provided even after a fault of the microcontroller occursand while the control of the power switch is performed solely by theswitch control circuit.

Further aspects and features of embodiments the present invention willbe learned from following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects and features of the present invention will become apparent tothose of ordinary skill in the art by describing, in detail, exemplaryembodiments thereof with reference to the attached drawings, in which:

FIG. 1 illustrates a schematic view of a battery system according to anembodiment;

FIG. 2 illustrates a schematic view of a battery system according to anembodiment;

FIG. 3 illustrates a schematic view of a switch control circuitaccording to an embodiment;

FIG. 4 illustrates a schematic view of a switch control circuitaccording to an embodiment; and

FIG. 5 illustrates a timeline of a current of a battery system accordingto an embodiment.

DETAILED DESCRIPTION

Reference will now be made, in detail, to embodiments, examples of whichare illustrated in the accompanying drawings. Aspects and features ofexemplary embodiments, and implementation methods thereof, will bedescribed with reference to the accompanying drawings. The presentinvention, however, may be embodied in various different forms andshould not be construed as being limited to the illustrated embodiments.Accordingly, processes, elements, and techniques that are not considerednecessary to those having ordinary skill in the art for a completeunderstanding of the aspects and features of the present invention maynot be described. Further, in the drawings, the relative sizes ofelements, layers, and regions may be exaggerated for clarity, and likereference numerals denote like elements such that redundant descriptionsthereof may be omitted.

It will be understood that, although the terms “first,” “second,” etc.,are used to describe various elements, these elements should not belimited by these terms. These terms are used to distinguish one elementfrom another element. For example, a first element may be named a secondelement and, similarly, a second element may be named a first elementwithout departing from the scope of the present invention.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Further, the use of “may”when describing embodiments of the present invention refers to “one ormore embodiments of the present invention.” In the following descriptionof embodiments of the present invention, the terms of a singular formmay include plural forms unless the context clearly indicates otherwise.Expressions, such as “at least one of,” when preceding a list ofelements, modify the entire list of elements and do not modify theindividual elements of the list. Also, the term “exemplary” is intendedto refer to an example or illustration. As used herein, the terms “use,”“using,” and “used” may be considered synonymous with the terms“utilize,” “utilizing,” and “utilized,” respectively. It will be furtherunderstood that the terms “includes,” “including,” “comprises,” and/or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof.

As used herein, the terms “substantially,” “about,” and similar termsare used as terms of approximation and not as terms of degree and areintended to account for the inherent deviations in measured orcalculated values that would be recognized by those of ordinary skill inthe art. Further, if the term “substantially” is used in combinationwith a feature that could be expressed as a numeric value, the term“substantially” denotes a range of +/−5%.

FIG. 1 illustrates a schematic view of a battery system 100 according toan embodiment of the present invention. The battery system 100 includesa plurality of battery cells 10 that are connected to each other inseries between a first node 11 and a second node 12. The battery cells10 may also be connected to each other in parallel between the firstnode 11 and the second node 12, thereby forming an XsYp configurationbetween the first and second nodes 11, 12. Further, battery submodulesmay be connected between the first and second nodes 11, 12 (e.g., thebattery cells 10 may be arranged into battery submodules between thefirst and second nodes 11, 12).

Each of the twelve battery cells 10 provides a voltage of approximately4 V, such that a voltage VDD of approximately 48 V is applied betweenthe first node 11 and the second node 12. An external load 14 issupplied with this voltage (e.g., with the VDD of approximately 48V) ofthe battery cells 10. A relay 13 is interconnected as a power switchbetween the first node 11 and the external load 14 for controlling thepower supply to the external load 14. The conductivity state of therelay 13 is controlled by a control unit (e.g., a controller) 20 via anoutput node 27 of the control unit 20.

The control unit 20 may include at least one input node for receivingsensor inputs. For example, as shown in FIG. 1, the control unit 20includes two input nodes 21 configured to receive differential inputs.These input nodes 21 are connected upstream and downstream,respectively, of ends of a shunt resistor 15 that is interconnectedbetween the second node 12 and the external load 14. Hence, the inputnodes 21 receive (or measure) a voltage drop over the shunt resistor 15as a sensor signal 40 (e.g., the input nodes 21 measure the voltage dropover the shunt resistor 15 and output the measured voltage drop as thesensor signal 40).

The control unit 20 further includes a front end circuit 22 forreceiving and processing the sensor signal 40 in order to generate astate signal 41 based on the sensor signal 40. In one embodiment, thestate signal 41 is indicative of a current I provided by the pluralityof battery cells 10 and is generated by utilizing a known value of theresistance R of the shunt resistor 15.

The control unit 20 further includes a microcontroller 24 that isconnected to the front end circuit 22 and receives the state signal 41from the front end circuit 22.

The microcontroller 24 is further configured to generate a first controlsignal 42 based on the state signal 41. The first control signal 42 isused to set the relay 13 into either a conductive or a non-conductivestate. For example, the microcontroller 24 generates a first controlsignal 42 that sets the relay 13 into the conductive state when thestate signal 41 indicates a current within the standard operationconditions of the battery system 100, and the microcontroller 24generates a first control signal 42 that sets relay 13 into thenon-conductive state when the state signal 41 indicates an overcurrent.

The microcontroller 24 further generates and outputs a fault signal 43that is indicative of an operational state of the microcontroller 24. Inone embodiment, the fault signal 43 is based on self-testing of themicrocontroller 24 and/or is based on internal error codes that occurmore than sporadically. The fault signal 43 is either indicative of anoperability of the microcontroller 24 (e.g., that the microcontroller 24is operating properly) or of a malfunction of the microcontroller 24.The fault signal may have one of two possible values, such as “0” or“1”.

The control unit 20 further includes a switch control circuit 25 that isconnected to the front end circuit 22 and the microcontroller 24. Theswitch control circuit 25 receives the state signal 41 as an input fromthe front end circuit 22. The switch control circuit 25 also receivesthe first control signal 42 and the fault signal 43 from themicrocontroller 24. The switch control circuit 25 is further connectedto the output node 27 of the control unit 20.

The switch control circuit 25 is configured to generate a second controlsignal 44 based on the received state signal 41. The second controlsignal 44 is used to set the relay 13 into either a conductive or anon-conductive state. The switch control circuit 25 generates a secondcontrol signal 44 that sets the relay 13 into the conductive state whenthe state signal 41 indicates a current within standard operationalconditions of the battery system 100 and generates a second controlsignal 44 that sets relay 13 in the non-conductive state when the statesignal 41 indicates overcurrent. To this end, the second control signal44 may be different than (e.g., may be a different signal than) thefirst control signal 42.

The switch control circuit 25 outputs either the first control signal 42or the second control signal 44 to the relay 13 via the output node 27.The switch control circuit 25 outputs one of these signals 42, 44through to the output node 27 based on the fault signal 43. Based on thevalue of the fault signal 43, for example, whether it is indicative ofan operability or a malfunction of the microcontroller 24, the switchcontrol circuit 25 selects one of the first and second control signal42, 44 and outputs the selected control signal 42, 44 to the relay 13via the node 27. Thus, the control unit 20 allows for continued controlof the relay 13 based on the sensor signal 40 even when themicrocontroller 24 has a malfunction and can no longer reliably controlthe relay 13.

FIG. 2 illustrates a schematic view of a battery system 100 according toa second embodiment. The control unit 20 of the battery system 100 shownin FIG. 2 differs from that of the first embodiment, whereas all othercomponents are the same or substantially the same.

The control unit 20 of the second embodiment differs from that of thefirst embodiment in that it further includes an amplification circuit 23that is interconnected between the input node 21 and the conductiveconnection between the front end circuit 22 and the switch controlcircuit 25. The amplification circuit 23 provides a bypass of the frontend circuit 22 and further allows the amplified sensor signal 41′ to besupplied to the switch control circuit 25. Hence, the hardware path ofthe control unit 20 between the input nodes 21 and the output node 27via the switch control circuit 25 is also independent of the operabilityof the front end circuit 22.

The control unit 20 of the second embodiment further differs in that itincludes a system basis chip (SBC) 26 that is connected to themicrocontroller 24 and the switch control circuit 25. The system basischip 26 is configured to monitor an operational state of themicrocontroller 24 and to generate and output a fault signal 43 that isindicative of an operability of the microcontroller 24. The system basischip 26 may also have typical functionalities of an SBC. When themicrocontroller 24 cannot provide a reliable fault signal 43, which maycause a serious malfunction, the system basis chip 26 may furtherimprove the reliability of the control unit 20 by generating the faultsignal 43 instead of the microcontroller 24.

FIG. 3 illustrates a schematic view of a switch control circuit 25. Theswitch control circuit 25 may be part of the control unit 20 accordingto the first or second embodiment. The switch control circuit 25provides the core functionalities of this circuit with a relativelysimple design.

The switch control circuit 25 includes a multiplexer 36 and a comparator31. The comparator 31 is configured to compare the state signal 41 (orthe amplified sensor signal 41′) with a threshold (e.g., a predeterminedthreshold). The comparator 31 may include a further input for receivingthe threshold. The comparator 31 outputs a second control signal 44 thatreflects whether or not the state signal 41 (or the amplified sensorsignal 41′) exceeds the threshold.

The multiplexer 36 has two data signal inputs and one control signalinput. The first control signal 42 is supplied to a first data signalinput of the multiplexer 36, and the output of the comparator 31 issupplied to a second data signal input of the multiplexer 36. The faultsignal 43 is supplied to the control signal input of the multiplexer 36.The multiplexer 36 outputs one of the first and second control signal42, 44 based on the value of the received fault signal 43.

FIG. 4 illustrates a schematic view of a switch control circuit 25according to another embodiment. The switch control circuit 25 may bepart of the control unit 20 according to the first or second embodiment.The switch control circuit 25 shown in FIG. 4 provides the corefunctionalities of this circuit and further functionalities related tothe first time period and the second time period as described above. Theoperation of the switch control circuit 25 according to this embodimentis described with reference to the timeline of an output current ofbattery system 100 as shown in FIG. 5.

The switch control circuit 25 according to this embodiment receives thestate signal 41 (or the amplified sensor signal 41′), the first controlsignal 42, and the fault signal 43 as inputs.

During a normal operation mode A (see, e.g., FIG. 5) of the batterysystem 100 and the control unit 20, the microcontroller 24 operateswithout fault and a maximum current I^(l) _(max) is allowed to beprovided by the battery system 100. During the normal operation mode,the fault signal 43 is indicative of the operability of themicrocontroller 24 and has the binary value “1”. The fault signal 43 issupplied to the multiplexer 36 as the control signal input and sets thedata signal input of the multiplexer 36 to the first data signal input1, which corresponds to the first control signal 42 that is suppliedfrom the microcontroller 24. Hence, during the normal operation mode A,the first control signal 42 is output to the relay 13 via themultiplexer 36 and the output node 27, and thus, the relay 13 iscontrolled by the microcontroller 24. The microcontroller 24 sets therelay 13 into a non-conductive state via the first control signal 42when the state signal 41 indicates a current that exceeds I^(l)max.

At time point B (see, e.g., FIG. 5), a failure occurs in themicrocontroller 24, and the failure is immediately realized by themicrocontroller 24 itself (see, e.g., FIG. 1) or by the system basischip 26 connected to the microcontroller 24 (see, e.g., FIG. 2). Hence,from the time point B, the fault signal 43 is indicative of amalfunction of the microcontroller 24 and has the value “0”. Thus, thecontrol signal input of the multiplexer 36 is set to the second datasignal input 0 via the fault signal 43.

Further, at the time point B, at least one second electrical consumer ofan electric vehicle that is supplied by (e.g., powered by) the batterysystem 100 and is not security relevant for the electric vehicle isdisconnected from the battery system 100 via a control unit, which maybe the system basis chip 26 shown in FIG. 2. Hence, as shown in FIG. 5,the current l (curved line) starts dropping from the time point B inorder to increase the safety of the electric vehicle.

The second data signal input 0 of multiplexer 36 is connected to thestate signal 41 (or the amplified sensor signal 41′) by a hardware pathdescribed in more detail below. In the control unit 20 as illustrated inFIG. 4, the relay 13 is set into the conductive state as long as itreceives a high signal “1” via the output node 27.

As a part of said hardware path, the second data signal input ofmultiplexer 36 is connected to the fault signal 43 via an OR gate 35 anda first latching element 32. The first latching element 32 receives thefault signal 43 as an input and transmits an output to the OR gate 35.The first latching element 32 latches a high input signal suppliedthereto for a second time period T₂ (e.g., a predetermined second timeperiod). As the value of the fault signal 43 changes from high to low attime point B of FIG. 5, the first latching element 32 outputs a highvalue “1” to a first input of the OR gate 35 until the second timeperiod T₂, which starts at the time point B, lapses. The OR gate 35outputs a high value “1” as long as a single input provided thereto ishigh and, thus, provides a high signal “1” to the second date signalinput 0 of the multiplexer 36 until the second time period T₂, whichstarts at the time point B, lapses.

As illustrated in FIG. 5, during the second time period T₂, for example,during initial mode C, the current drops below a second currentthreshold I^(ll) _(max) due to cutting the security irrelevant secondelectrical consumers off from the battery system 100. During the initialmode C, threshold based control of the relay 13 does not occur in orderto reduce the current consumption below I^(ll) _(max) while preventing(or reducing the risk of) a premature shut down of the battery system100 via the relay 13.

After the second time period T₂ lapses, which started at the time pointB, the first latching element 32 no longer provides a high signal “1” tothe first input of the OR gate 35. Thus, whether or not the OR gate 35outputs a high signal “1” to the multiplexer 36 solely depends on thesignal applied to a second input of the OR gate 35. The second input ofthe OR gate 35 receives an output signal of an AND gate 34, the inputsof which are described below.

A second input of the AND gate 34 is connected to the fault signal 43via a second latching element 33. The second latching element 33 latchesa high input signal supplied thereto for a first time period T₁ (e.g., apredetermined first time period T₁). As the value of the fault signal 43changes from high to low at the time point B of FIG. 5, the secondlatching element 33 outputs a high value “1” until the lapse of thefirst time period T₁, which started at the time point B. Thus, at theend of the first time period T₁, for example, at point G illustrated inFIG. 5, the second latching element 33 outputs a low signal “0” to theAND gate 34, and thus, the AND gate 34 also outputs a low signal “0” tothe multiplexer 36. Hence, at the point G, the availability mode of thebattery system 100 that started with the fault at time point B ends andthe battery system 100 is inevitably shut down by setting the relay 13into a non-conductive state.

A first input of the AND gate 34 is connected to the comparator 31, asdescribed above with respect to FIG. 3, and the comparator 31 receivesthe state signal 41 (or the amplified sensor signal 41′) and outputs asecond control signal 44 based on a comparison between the signal 41 or41′ and a threshold (e.g., a predetermined threshold). The comparator 31outputs a high signal “1” when the state signal 41 (or the amplifiedsensor signal 41′) indicates a current below threshold current I^(ll)_(max) as illustrated in FIG. 5 and outputs a low signal “0” when thestate signal 41 (or the amplified sensor signal 41′) indicates a currentabove threshold current I^(ll) _(max) as illustrated in FIG. 5.

Hence, during the first time period T₁ and after the lapse of the secondtime period T₂, for example, between the points D and G or duringlow-performance mode E as illustrated in FIG. 5, sensor-based control ofthe relay 13 is performed in order to provide overcurrent protection,whereas the overcurrent is lowered from I^(l) _(max) to I^(ll) _(max).In other words, during the low-performance mode E, the battery system100 is shut down via the relay 13 when the state signal 41 (or theamplified sensor signal 41′) indicates a current above the thresholdcurrent I^(ll) _(max).

The latching times of the latching elements 32 and 33 (e.g., the firsttime period T₁ and the second time period T₂), may be counted by timers.The timers for counting the first time period T₁ and the second timeperiod T₂ may be started at the time when a fault of the microcontroller24 is recognized.

The electronic or electric devices and/or any other relevant devices orcomponents according to embodiments of the present invention describedherein may be implemented utilizing any suitable hardware, firmware(e.g. an application-specific integrated circuit), software, or acombination of software, firmware, and hardware. For example, thevarious components of these devices may be formed on one integratedcircuit (IC) chip or on separate IC chips. Further, the variouscomponents of these devices may be implemented on a flexible printedcircuit film, a tape carrier package (TCP), a printed circuit board(PCB), or formed on one substrate. The electrical connections orinterconnections described herein may be realized by wires or conductingelements, e.g., on a PCB or another kind of circuit carrier. Theconducting elements may include metallization, for example, surfacemetallization and/or pins, and/or may include conductive polymers orceramics. Further, electrical energy may be transmitted via wirelessconnections, for example, by using electromagnetic radiation and/orlight.

Further, the various components of these devices may be a process orthread, running on one or more processors, in one or more computingdevices, executing computer program instructions and interacting withother system components for performing the various functionalitiesdescribed herein. The computer program instructions are stored in amemory which may be implemented in a computing device using a standardmemory device, such as, for example, a random access memory (RAM). Thecomputer program instructions may also be stored in other non-transitorycomputer readable media such as, for example, a CD-ROM, flash drive, orthe like.

Also, a person of skill in the art should recognize that thefunctionality of various computing devices may be combined or integratedinto a single computing device, or the functionality of a particularcomputing device may be distributed across one or more other computingdevices without departing from the scope of the exemplary embodiments ofthe present invention.

SOME REFERENCE NUMERALS

10 battery cell

11 first node of battery system

12 second node of battery system

13 power switch (relay)

14 external load

15 sensor (shunt resistor)

20 control unit

21 input node

22 front end circuit

23 amplification circuit

24 microcontroller

25 switch control circuit

26 system basis chip

27 output node

31 comparator circuit

32 first latching element

33 second latching element

34 “AND” gate

35 “OR” gate

36 multiplexer

40 sensor signal

41 state signal

42 first control signal

43 fault signal

44 second control signal

What is claimed:
 1. A control unit for a battery system comprising aplurality of battery cells, the control unit comprising: an input nodeconfigured to receive a sensor signal indicative of a state of at leastone of the plurality of battery cells; a microcontroller connected tothe input node and configured to generate a first control signal basedon the sensor signal; and a switch control circuit configured to controla power switch of the battery system by: receiving the sensor signal,the first control signal, and a fault signal indicative of anoperational state of the microcontroller; generating a second controlsignal based on the sensor signal; and transmitting one of the firstcontrol signal and the second control signal to an output node of thecontrol unit based on the received fault signal.
 2. The control unitaccording to claim 1, wherein the switch control circuit is configuredto: transmit the first control signal to the output node when the faultsignal indicates the microcontroller is operative; and transmit thesecond control signal to the output node when the fault signal indicatesthe microcontroller is malfunctioning.
 3. The control unit according toclaim 1, further comprising a front end circuit interconnected betweenthe input node and the microcontroller and configured to generate astate signal based on the sensor signal, wherein the microcontroller isconfigured to generate the first control signal based on the statesignal, and wherein the switch control circuit is configured to receivethe state signal and to generate the second control signal based on thestate signal.
 4. The control unit according to claim 3, furthercomprising an amplification circuit interconnected between at least twoof the input node, the front end circuit, and the switch controlcircuit, wherein the switch control circuit is configured to generatethe second control signal based on the state signal.
 5. The control unitaccording to claim 1, wherein the switch control circuit is a hardwarepath with an failure-in-time (FIT) rate of 100 or less.